docs: def _add_dns_records(self, conf, mgmts):
          """
          Add DNS records dict('dns_records') to ``conf`` for each
          management network. Add DNS forwarder IP('dns_forward') for each none
          management network.
  
  
          Args:
              conf(spec): spec
              mgmts(list): management networks names
  
          Returns:
              None
          """
  
          nets = conf['nets']
          dns_mgmt = mgmts[-1]
          LOGGER.debug('Using network %s as main DNS server', dns_mgmt)
          forward = conf['nets'][dns_mgmt].get('gw')
          dns_records = {}
          for net_name, net_spec in nets.iteritems():
              dns_records.update(net_spec['mapping'].copy())
              if net_name not in mgmts:
                  net_spec['dns_forward'] = forward
  
          for mgmt in mgmts:
              if nets[mgmt].get('dns_records'):
                  nets[mgmt]['dns_records'].update(dns_records)
              else:
                  nets[mgmt]['dns_records'] = dns_records